The present invention relates to a locking device particularly usable for wheels of skates of the type which comprises a supporting frame for a shoe, between the wings of which two or more mutually in-line wheels are freely pivoted.
A problem currently felt in conventional skates is substantially the fact that it is impossible for the user to simply walk unless he removes the skates.
As a partial solution to this problem, U.S. Pat. No. 2,725,238 discloses a skate having a first supporting plate for a shoe, below which two mutually parallel pairs of wheels are pivoted.
The skate has a screw engaging a brake constituted by a second plate which is interposed between the shoe supporting plate and the rolling surfaces of the two pairs of wheels. The screw actuates a vertical movement of the second plate and thus allows the plate to interact with the rolling surface of the wheels so as to limit their rotation.
The skate has the drawback that it is necessary to operate the screw, which has a head which can be gripped by the user, arranged below the second plate and therefore in a region which is difficult to access. Moreover, wheel locking occurs after intense pressure, which can be applied to the wheels by means of the second plate, therefore requiring application of a large number of turns to the screw, which takes a long time and is awkward because of the position of the screw.
U.S. Pat. No. 3,900,203 discloses a skate which has a shoe supporting frame provided with two wings which are mutually parallel and are directed towards the ground.
Two pairs of wheels are pivoted between the wings and are mutually connected in pairs by two auxiliary plates which have, in the interspace between two adjacent wheels, holes which also pass at the wings of the frame and accommodate the shank of a screw which is threaded at one end and is connected to a knob arranged externally to one of the wings of the frame.
A rotation applied to the knob forces the deformation of at least one of the two auxiliary plates, whose flexing makes the auxiliary plate interact with the surface of a disk associated with the hub of the wheels, thus obtaining a braking effect.
Also this solution is not ideal, since it is not easy for the user to turn the knob. Moreover, it is necessary to apply a considerable force to achieve the mutual locking of the two elements.
Moreover, this solution has shown less than perfect efficiency over time, owing to the wear of the materials placed in mutual contact, which are in any case subject to slight friction even when the user walks.
U.S. Pat. No. 4,312,514 discloses a skate which has a shoe supporting plate and below which two pairs of wheels, arranged parallel to each other, are freely pivoted.
In this solution it is possible to lock each one of the pairs of wheels, since on each one there are provided two rollers which are arranged transversely to the wheels and can be moved into contact with the rolling surface of the wheels by activating a suitable washer which is rotatably associated with a complementarily threaded shank which is coupled, at one end, to the pivot of the wheels and passes at the specifically provided seat formed in a roller connecting element.
Also this solution suffers the above-mentioned drawbacks and therefore entails difficulty in activating the washers arranged below the shoe supporting plate and the considerable time required to activate said washers; to make matters worse, there are two washers.
U.S. Pat. No. 5,503,433 discloses a skate which has a shoe supporting frame and comprises two mutually parallel lateral wings, between which four wheels are freely pivoted.
This solution uses, as an element for locking the rotation of the wheels, a cable which is closed in a loop and can be locked, at one end, at the interspace between the base of the frame and the first front wheel, while suitable cylinders are associated transversely to the cable and can be interposed in the gap between two mutually adjacent wheels. The last cylinder can be arranged at the end of the frame that lies above the rear wheel.
This solution, however, is scarcely safe in terms of user protection, because the force that can be applied by the rollers does not ensure perfect locking of the wheels. The locking action in fact cannot be adjusted in any way by the user to adapt it for example to his physical characteristics, such as his/her weight. Moreover, the cable must be carried by the user, must be stored and may be lost.
U.S. Pat. No. 5,511,805 discloses a skate which has a shoe supporting frame and comprises two lateral wings, between which wheels are freely pivoted and are thus arranged mutually in-line.
An auxiliary wheel truck is located between the lateral wings of the frame and is fixed to the lateral wings by means of an actuation screw which alters its position transversely to the frame.
Changing the position of the truck by means of the screw causes the auxiliary wheels, which lie in the interspace between two adjacent wheels, to interact with the latter wheels, thus locking their movement.
However, this solution too entails the above-mentioned drawbacks, since wheel locking is awkward and requires a long time to be performed owing to the need to turn the screw several times.